This multi-series chart combines bar and line encodings to compare financial metrics of a fictional company across years, highlighting revenue and expenses as bars against profit and employee counts as overlaid lines. Built with React and D3 v6, the visualization uses separate y-scales for bars and each line series, with axes rendered via `axisLeft`, `axisRight`, and `axisBottom` on an SVG. The code employs `scaleBand` and multiple `scaleLinear` instances, then draws bars as `rect` elements and lines using D3's `line` generator, with gridlines created from a reused left axis.